There have been few efforts to examine how the planning process affects the outcome of a terrorist plot. This research brief provides some preliminary findings from an examination of the impact of the length of the planning process, the impact of multiple participants, and the volume of precursor activity on the success or failure of terrorist plots in the United States. While conventional wisdom holds true that a shorter planning process and fewer preparatory activities reduces perpetrators chances of getting caught therefore increases success rate, the new findings show that the more people involved in the planning process also increases the probability of success